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Bacterial-growth inhibiting properties of multilayers formed with modified polyvinylamine
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.ORCID iD: 0000-0003-1812-7336
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.ORCID iD: 0000-0001-8622-0386
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
2011 (English)In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 88, no 1, 115-120 p.Article in journal (Refereed) Published
Abstract [en]

New methods are needed to fight antibiotic-resistant bacteria. One alternative that has been proposed is non-leaching, permanently antibacterial surfaces. In this study, we test multilayers formed with antibacterial cationic polyvinylamine (PVAm) and polyacrylic acid (PAA) in a growth-inhibition assay. Both hydrophobically modified and native PVAm were investigated. Multilayers did reduce the bacterial growth, as compared to single layers. However, the sampling time in the assay was critical, as the treated surface area is a capacity-limiting factor. After 2 h incubation, a maximal growth inhibition of more than 99% was achieved with multilayers. In contrast, after 8 h we observed a maximal growth-inhibition of 40%. At longer incubation times, the surface becomes saturated, which explains the observed time-dependent effectiveness. The polymers giving multilayers with the strongest growth-inhibiting properties were native PVAm and PVAm modified with C(8), which also were the polymers with highest charge density. We therefore conclude that this effect is mainly an electrostatically driven process. Viability staining using a fluorescent stain showed a high viability rate of the adhered bacteria. The multilayers are therefore more bacteriostatic than antibacterial.

Place, publisher, year, edition, pages
2011. Vol. 88, no 1, 115-120 p.
Keyword [en]
Polyvinylamine, Hydrophobic modification, Polyacrylic acid, Polyelectrolyte multilayers, Antibacterial surfaces
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-25252DOI: 10.1016/j.colsurfb.2011.06.023ISI: 000295344800015Scopus ID: 2-s2.0-80052083682OAI: oai:DiVA.org:kth-25252DiVA: diva2:356829
Note
QC 20101014 Updated from submitted to published.Available from: 2010-10-14 Created: 2010-10-14 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Development of New Bacteria-Reducing Surfaces
Open this publication in new window or tab >>Development of New Bacteria-Reducing Surfaces
2009 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In recent years, antibacterial surfaces have been a subject of increased interest. Especiallyinteresting are non-leaching, contact-active surfaces that physically disrupts the bacterialcell using immobilised cationic polymers. Thus the risks of bacterial resistance and discharge of hazardous biocides is minimised. The assembly of such surfaces is elaborate andusually involves organic solvents. Here, polyelectrolyte multilayers (PEM) are proposed as an effective surface modification method, with an overall goal of producing antibacterial cellulose fibres. The PEM process is based on physical adsorption of oppositely charged polymers in aqueous solutions. Multilayers were formed with the bactericidal polymer polyvinylamine (PVAm) and polyacrylic acid. PVAm compounds with hydrophobic modificationswere applied as well, as they possess increased antibacterial activity in solution.

In this work, the multilayer formation was studied on model surfaces of silicone oxide and glass in order to obtain fundamental knowledge of the polymer system. QCM-D and reflectometry, which detect total mass including bound water and polymer mass only, respectively, were used to analyse the layer formation. Salt-concentrations were varied at 1, 10 or 100 mM NaCl. A stepwise multilayer formation with exponential-like polymer adsorption but with decreasing water content for each layer was seen at all salt concentrations.A higher salt concentration resulted in an increased adsorbed mass. No significant differences in adsorption between the modified and unmodified PVAm could be detected. AFM imaging applied to multilayers having nine layers showed large surface aggregates under high salt conditions for the C6-modified PVAm. Dynamic light scattering showed that the polymer occurred as single molecules in solution; hence it was concluded that theaggregation is surface-associated.

The multilayers were then tested for bacterial growth inhibition. The relative bacterial inhibition was time-dependent, as the surface was saturated with bacteria over time. After two hours, a maximal inhibition of 99 % could be observed for the multilayers. After eight hours, a moderate inhibition of less than 40 % was detected. Using multilayers affected the results positively compared to single layers. After three layers, though, no further reductionwas seen. Viability staining of the surface-adhered bacteria revealed that the adhered bacteria had intact membranes. Therefore, the microbiological properties of the multilayers can at this point be described more as growth-inhibiting by bacterial adhesion effectsthan as biocidal. However, this work has shown the importance of combining surface characterisation and microbial testing to understand the bacteria-surface interaction.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. 36 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2009:25
Keyword
antibacterial, polyelectrolyte multilayers, polyvinylamine
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-10586 (URN)978-91-7415-340-8 (ISBN)
Presentation
2009-06-05, STFI-salen, KTH, Drottning Kristinas väg 6, Stockholm, Innventia, 14:00 (Swedish)
Opponent
Supervisors
Projects
Biointeractive fibres
Available from: 2009-06-08 Created: 2009-05-28 Last updated: 2010-10-14Bibliographically approved
2. The creation of antibacterial fibres through physical adsorption of polyelectrolytes
Open this publication in new window or tab >>The creation of antibacterial fibres through physical adsorption of polyelectrolytes
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Contact-active antibacterial surfaces with irreversibly attached antibacterial com-pounds are a sustainable alternative to traditional biocides. No chemicals are released into nature and the antibacterial mechanism reduces the risk of the evolution of re-sistant bacteria. However, the preparation of such surfaces is far from sustainable, as organic solvents and harsh reaction conditions commonly are required. An alter-native option is to use polyelectrolyte multilayers (PEM), based on physical ad-sorption, which can be performed in water-based solutions at room temperature. Although contact-active antibacterial PEMs have been reported previously, this is the first study of renewable cellulosic wood fibres.

The build-up of cationic polymer polyvinylamine (PVAm) and anionic polyacrylic acid (PAA) multilayers on model surfaces was studied to optimise adsorption. The amount of adsorbed polyelectrolytes was continuously growing with increasing number of layers, but remained dense and flat as the number of layers increased. The largest adsorption was obtained at a high salt concentration, which shielded the repulsion between the polymers.

Model surfaces were also used to evaluate the influence of the polymer and number of layers on the antibacterial properties. Multilayers on model surfaces showed a low bacteriostatic effect, with up to approximately 40 % inhibition for 3 layers of un-modified PVAm/PAA. In contrast, when the same multilayers were applied on cel-lulosic fibres, bacterial-growth inhibition of > 99.9% was obtained. Hydrophobically modified PVAm did not yield better results, despite being superior in solution. An increase in fibre charge by fibre oxidation led to the largest amount of adsorbed pol-ymer and the best antibacterial properties, an effect that lasted for weeks. Electron microscopy study of bacteria on the fibres showed that the bacteria interacted more on a highly charged surface and that the morphology of the bacterial cell could be affected. The effect was suggested to be due to electrostatic interaction with the pos-itively charged modified fibres. The promising results offer the possibilities of a new generation of antibacterial surfaces based on a renewable resource.

Abstract [sv]

Antibakteriella kontaktaktiva ytor som har ett antibakteriellt ämne permanent fäst på ytan är ett miljövänligt och säkrare alternativ till traditionell biocidanvändning. Inget utsläpp av giftiga ämnen sker från ytorna och detta tillsammans med den anti-bakteriella mekanismen minskar risken för att bakterierna utvecklar resistens. Till-verkningsprocessen i sig har dock hittills varit allt annat än miljövänlig, då den ke-miska modifieringen kräver organiska lösningsmedel och har reaktioner som kräver speciella villkor, t ex höga temperaturer. En alternativ ytmodifiering är att använda sig av fysikalisk adsorption av polyelektrolyter i multiskikt, eftersom detta kan göras i vat-tenlösningar och i rumstemperatur. Det här arbetet är det första som beskriver kon-takt-aktiva multilager på förnyelsebara svedbaserade cellulosafiber.

Som ett första steg gjordes en adsorptionsstudie på modellytor för att optimera ad-sorptionen av katjonisk polyvinylamin (PVAm) och anjonisk polyakrylsyra (PAA). Med ökande antal lager ökade totala mängden adsorberad polymer samtidigt som multilagerna förblev platta och täta. Den högsta adsorptionen skedde vid en hög salt-halt som minimerade den elektrostatiska repulsionen mellan polymerkedjorna.

Modellytor användes även för att studera hur de antibakteriella egenskaperna påver-kades av polymermodifiering och av antal lager. På dessa ytor uppmättes en låg bakte-riostatisk effekt med upp till 40 % inhibering av bakterietillväxten för tre lager av PVAm./PAA När däremot samma multilager fanns på cellulosafiber ökade in-hiberingen till uppemot 99.9 %. Hydrofobmodifiering av PVAm påverkade inte det antibakteriella resultatet när de var i multilager, trots bevisad ökad verkan i lösning. Genom att via oxidering öka fiberladdningen kunde mängden adsorberad polymer yt-terligare öka och resulterade i en förbättrad antibakteriell verkan som höll i sig i flera veckor. Elektronmikroskopi av bakterier på fiber visade en ökad interaktion med hög-laddade ytor och att bakteriernas cellmorfologi kan påverkas av ytorna.Den observerade antibakteriella effekten föreslås vara en följd av elektrostatisk inter-aktion mellan de negativt laddade bakterierna och positivt laddade modifierade fibrena. Resultaten är lovande och banar väg för nya kontakt-aktiva antibakteriella material.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. 58 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2012:11
Keyword
antibacterial, polyelectrolyte multilayers, polyvinylamine, contact-active antibacterial surfaces
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-90731 (URN)978-91-7501-274-2 (ISBN)
Public defence
2012-03-16, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Projects
Biointeractive fibres with antibacterial properties
Available from: 2012-02-28 Created: 2012-02-28 Last updated: 2013-02-25Bibliographically approved

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Illergård, JosefinWågberg, Lars

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